1. Field of the Invention
This invention relates in general to well tubulars and hangers and, in particular, to a lockdown bushing for increased tubular lockdown capacity and a method to operate the same.
2. Brief Description of Related Art
Typically, a lockdown bushing may be run downhole to land and set above a casing hanger to provide additional casing lockdown capability. The lockdown bushing may be needed due to thermal expansion of the casing string. Lockdown bushings improve long-term seat reliability below the lockdown bushing by sharing the cyclic axial loads applied to the casing hanger. To properly land and set a lockdown bushing, the lockdown bushing is typically run proximate to lock-ring grooves formed in the subsea wellhead axially above the casing hanger. Generally, the operation requires running of a lead impression tool prior to running and setting of the lockdown bushing. The lead impression tool determines the elevation of the lock-ring grooves for proper landing of the lockdown bushing. However, this step is often bypassed due to the costs associated with performing an additional tool trip with the drilling rig. Typically, the lockdown bushing is run, landed, and set without checking the locking ring groove elevation.
If there is a problem with the lockdown bushing, the lockdown bushing may then be removed and the elevation of the locking ring grooves checked with the lead impression tool. This adds additional downhole trips and can significantly increase the costs associated with completion of a well. Where the lead impression tool is used, the well casing will have a reduced capacity for handling upward axial loads until the lockdown bushing is installed. This can make the well more vulnerable to blowouts for a longer period of time. Still further, many lockdown bushings do not have a sufficient capacity to resist upward axial forces applied to the casing hangers in some deeper well installations. Therefore, there is a need for a single-trip lockdown bushing that may be run without a lead impression tool that also has a greater load capacity than those known in the art.